High quality lead-free perovskites toward white light emitting diodes and X-ray imaging

Abstract

Lead-free metal halide perovskites have become emerging candidates for white light emitting diodes and X-ray imaging, and exploration of the corresponding down-conversion phosphors and scintillators based on perovskite structures with a high-performance for advanced devices is ongoing. Here, we synthesized Cs₂HfCl₆: Te⁴⁺ crystals with a yellow emission at 557 nm and a wide full width at half maximum around 104 nm, which is attributed to the transition from the triplet state to the ground state (³P₁ → ¹S₀) of Te⁴⁺ ions. Moreover, the energy transfer process from the self-trapped exciton of Cs₂HfCl₆ to Te⁴⁺ ions is demonstrated. Accordingly, the white light emitting diodes show a color rendering index of 61.8, which was manufactured by employing the Cs₂HfCl₆:3% Te⁴⁺ crystals with a photoluminescence quantum yield of 74.2%. Furthermore, the Cs₂HfCl₆: Te⁴⁺ crystals exhibit a fascinating steady-state X-ray light yield reaching 76,194 photons MeV⁻¹, a low detection limit of 36.2 nGy s⁻¹ and a high spatial resolution of 11 lp mm⁻¹. Hence, this study offers new insight for the development of lead-free metal halide perovskites and promotes their versatile application in white light emitting diodes and X-ray imaging.